Polyglycol esters



United States Patent 3,330,764 POLYGLYCOL ESTERS Robert J. Nankee,Midland, Mich assignor to The Dow Chemical Company, Midland, Mich, acorporation of Delaware No Drawing. ()riginal application June 15, 1962,Ser. No. 202,722, now Patent No. 3,206,486. Divided and this applicationJune 4, 1965, Ser. No. 474,196

2 Claims. (Cl. 25276) This case is a division of application Serial No.202,722, now Patent No. 3,206,486.

This invention relates to long-chain unsaturated fatty acid monoestersof polyoxypropylene-polyoxyethylene block copolymer glycols, to improvemethods for making such esters and to brake fluids and lubricantscomprising said esters.

Brake fluids must meet many requirements, among the most critical ofwhich are lubricity, non-corrosiveness and compatibility with othercommercial brake fluids. Failure in any one of these properties rulesout a fluid regardless of its score on other properties. The fluids ofthe present invention are outstanding in the above properties, inaddition to amply meeting all other commercial and militaryrequirements.

The polyglycol esters of this invention are those having the formula:

wherein R is a straight-chain aliphatic hydrocarbon radical containing17 carbon atoms and 1 to 2 olefinic double bonds, P is a 1,2-propyleneradical, E is an ethyl ene radical, in is an integer about to 20, n isan integer about 3 to 8 and the ratio m/n is about 2.2 to 4.3.

Esters of the above type are most conventiently made by condensing afatty acid having the formula RCOOH, such as oleic or linoleic acid, ora mixture of such acids, with about 10 to 20 molecular equivalents ofpropylene oxide and then condensing the thus formed product with about 3to 8 molecular equivalents of ethylene oxide. The general technique ofcarrying out such a synthesis, as well as alternative syntheses, arewell known in the art. Particularly valuable esters of the above typeare those in which the acyl radical, RCO, is derived from tall oil fattyacids. Such acids are derived from tall oil and consist of at leastabout 90 percent of fatty acid, the predominant constituents of whichare oleic and linoleic acids. Other sources of suitable acids includethe unsaturated fractions of lard, tallow, corn oil, cottonseed oil andthe like.

The most widely used process for condensing an alkylene oxide with acompound containing an active hydrogen atom, a fatty acid being atypical such compound, is to contact the reactants at a suitabletemperature, such as about 50 to 200 C., in the presence of an alkalicatalyst. The alkali may then be left in the final product if itspresence is unobjectionable. More often it is neutralized by reactionwith an acid, an alkyl halide, an alkylene halohydrin or the like. Thealkali catalyst is usually sodium or potassium or the oxide, hydroxideor a lower alkoxide of one of these alkali metals. While suchneutralization processes are adequate to adjust the pH of the product tothe desired value, they are in general objectionable because theyproduce as a by-product a salt that is often difiicult to separate fromthe product.

Such salts are frequently of a corrosive nature and may also exert anundesirable influence on the reactions and properties of the product inits later uses.

It is a special feature of the present invention that when a fatty acid,such as tall oil, is condensed with an alkylene oxide in the presence ofan alkali catalyst, the above difliculties arising from the presence ofthe catalyst in the product can be readily avoided by neutralizing thecatalyst by reaction with more of the same or a similar fatty acid. Theby-product of such neutralization is the alkali metal salt of the fattyacid and is in general soluble in the product and contributes noundesirable properties thereof. Indeed, when the product is to be usedin brake fluids, the presence of the fatty acid salt is actually anadvantage since it contributes lubricity and inhibits metal corrosion bythe brake fluid. In a preferred embodiment of this aspect of theinvention, potassium oxide, hydroxide or alkoxide is mixed with tall oilfatty acid, propylene oxide and ethylene oxide are then condensed withthe acid in sequence, and finally the catalyst is neutralized by theaddition of approximately the stoichiometric amount of tall oil acid.The product thus obtained, containing about 0.1 to 2 percent by weightof the fatty acid salt, is exceptionally effective as a lubricant inbrake fluids and similar hydraulic fluids and lubricants.

The practice of the invention is illustrated by the following examples.

One molecular equivalent of tall oil fatty acid percent fatty acidcontent; predominantly oleic and linoleic acids) was placed in areactor, 0.04 percent by weight of KOH was added, the reactor was heatedto 125 C. and held at this temperature while 14.1 molecular equivalentsof propylene oxide were sparged into the reaction mixture. When all thepropylene oxide had reacted, 4.7 molecular equivalents of ethylene oxidewere similarly added.

When the above reactions were completed, the catalyst was neutralized bythe addition of tall oil fatty acid to a pH of 6.5 as measured in a 50percent solution in 1:1 methanol-water. The product was thendevolatilized under vacuum.

The final product was an oily liquid having a viscosity of 90.0centistokes at F. and 15.3 centistokes at 210 F. and a viscosity indexof 144. Its pour point was 30 F., at which point it remained clear.

A typical brake fluid based on the above product is as follows:

Component: Parts by wt. The above tall oil ester 12 Polypropylene glycol(mol. wt. 4000) 8 Dipropylene glycol 10 Z-Ethoxyethoxyethanol 70 Theabove tall oil esters exhibit exceptional lubricity, especially in thestick-slip test. This test evaluates both the static (stick) and thekinetic (slip) friction between intermittently moving surfaces, such as,for example, the movement of a piston in a cylinder. In addition, theyare compatible with all commercial brake fluids, have very littleswelling effect on rubber and are non-corrosive to the common metalsused in hydraulic systems.

Similarly valuable esters are obtained as described above by the blockpolymerization of 10 to 20 moles of propylene oxide followed by 3 to 8moles of ethylene oxide, these oxides being sequentially condensed withtall oil fatty acids or with other similar fatty acids containing 1 to 2olefinic double bonds. In choosing the proportions of the two alkyleneoxides it is important to have the ratio of the two within the range ofabout 2.2 to 4.3 because it is below 2.2 the product has an undesirablyhigh pour point. On the other hand, when the ratio exceeds about 4.3 theproduct becomes less compatible with other common brake fiuidcomponents, tolerates less Water and also has a greater tendency toswell rubber.

I claim:

1. A composition of matter consisting essentially of (a) an ester havingthe formula wherein RC0 is an acyl radical of a tall oil fatty acid, Ais a 1,2-propylene radical, E is an ethylene radical m and n areintegers, in being 10-20, n being 3-8 and m/n being 2.2 to 4.3, and (b)about 0.1 to 2% by weight, based on said ester, of an alkali metal saltof a tall oil fatty acid.

2. A composition as defined in claim 1 wherein the alkali metal ispotassium.

References Cited LEON D. ROSDOL, Primary Examiner.

JULIUS GREENWALD, SAMUEL H. BLECH,

Examiners.

I. T. FEDIGAN, Assistant Examiner.

1. A COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF (A) AN ESTER HAVINGTHE FORMULA